The partial oxidation process is a well known process for converting liquid hydrocarbonaceous and solid carbonaceous fuels into synthesis gas reducing gas, and fuel gas, i.e. gaseous mixture comprising H.sub.2 +CO. See coassigned U.S. Pat. Nos. 3,988,609 and 4,251,228 for example, which are incorporated herein by reference.
Ash-containing heavy liquid hydrocarbonaceous fuels i.e. reduced crude oil and ash-containing solid carbonaceous fuels i.e. coal or petroleum coke are desirable low-cost feedstocks for the partial oxidation process. However, when these fuels are used, the hot effluent gas stream from the reaction zone contains an increased amount of entrained molten slag and ash. In designs for the partial oxidation synthesis gas process that include a radiant and a convection gas cooler which are connected by a gas transfer line, the molten slag and ash entrained in the effluent gas stream may deposit on the inside walls of the gas transfer time. Over a period of time, the build-up of these deposits, which usually take place at areas of high turbulence, may lead to plugging in the gas transfer time. This problem and others may be avoided by the subject process thereby resulting in reduced downtime and lower maintenance costs. Convectively cooling partially cooled synthesis gas in a water jacketed transfer line convection cooler is described in coassigned U.S. Pat. No. 4,436,530, which is incorporated herein by reference. However, this scheme does not address applicants' problem of preventing the build-up of slag and ash deposits in sections of the gas transfer line where high gas turbulence occurs. Nor is heat recoverable at two different temperature ranges from the gas stream passing through the gas transfer line.